Steam control apparatus



April 4, 1967 J. D. DICKINSON ETAL 3,312,064

STEAM CONTROL APPARATUS Filed March 31, 1965 INVENTORS John D. Dickinsonand Lawrence K. Koering' United States Patent Ofitice 3,312,064 PatentedApr. 4, 1967 3,312,064 STEAM CONTROL APPARATUS John D. Dickinson,Springfield, Pa., and Lawrence K.

Koering, Elk Township, Ewan, N.J., assignors to Westinghouse ElectricCorporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar.31, 1965, Ser. No. 444,363 6 Claims. (Cl. 60-64) This invention relatesto steam control apparatus, more particularly to apparatus forcontrolling and regulating the temperature of superheated steam by waterinjection, and has for an object to provide improved apparatus of thistype.

In steam turbine power plants, gland structure encompassing the rotorshaft of a low pressure turbine expanding steam to a sub-atmosphericpressure is provided in the turbine housing to minimize leakage ofatmospheric air past the shaft into the turbine exhaust area. In orderto enhance the sealing characteristics of the gland structure, steam ata higher pressure than the internal steam pressure is introduced to thegland structure. The sealing steam may be taken from any suitablesource. However, for economic reasons it is usually taken from a higherpressure and temperature region in the steam turbine cycle and cooled tothe required temperature range by water spray before admission to thegland structure.

During operation, due to varying load on the power plant, thetemperature of the gland supply steam may vary considerably, and if thetemperature of the supply steam falls to a value below that required bythe gland, or if an excess of water is injected into the steam line dueto malfunction of the water injection control system, the

thermal shock on the turbine rotor shaft occasioned by the excessivecooling effect of the undesirably low temperature steam or slugs ofwater can cause warping of the turbine rotor shaft with attendantpossibility of serious damage due to resulting vibration of the rotorand/ or blade rubbing.

Accordingly, it is an object of the invention to provide apparatus forregulating the temperature of steam to a steam turbine rotor glandstructure by water injection and effective upon drop in temperature ofthe gland structure to a predetermined or unsafe value to automaticallytake corrective action and/ or initiate an alarm indicating such unsafecondition.

A further object is to provide apparatus of the foregoing type whereinthe corrective action is effected by an emergency water valve structurein the event of malfunction of a primary water control valve and/or itsas! sociated controls.

Another object is to provide apparatus for regulating the temperature ofsteam to a steam turbine rotor gland structure by Water injection andelfectiveupon rise in temperature of the gland structure to apredetermined or unsafe temperature to automatically take correctiveaction and/or initiate an alarm indicating such unsafe condition.

Briefly, in accordance with the invention, there is provided a primaryvalve for regulating the rate of water injection into a steam supplyconduit for a turbine rotor gland structure in such a manner that thesteam is cooled to a temperature range suitable for sealing the glandstructure. This valve is controlled by a first thermostatic meansresponsive to temperature of the gland structure.

There is also provided a secondary valve for overriding the primaryvalve and effective to assume control of the water injection in theevent of malfunction of the primary valve system causing a drop intemperature of the gland structure to a predetermined or unsafe value.The secondary valve is controlled by a second thermostatic means and isnormally in the open or unblocking position but is movable to the closedor blocking position upon such drop in temperature.

The second thermostatic means is also effective to initiate an alarmupon rise in temperature to a predetermined or unsafe value, therebyalerting an attendant to such condition.

The above and the objects are effected by the invention as will beapparent from the following description and claims taken in connectionwith the accompanying drawings, forming a part of this application, inwhich:

The sole figure is a diagrammatic view illustrating a steam turbinegland structure equipped with sealing steam control apparatus inaccordance with the invention.

Referring to the drawing in detail, there is shown a fragmentary portionof a steam turbine comprising a housing generally designated 10 having acircular aperture 11 provided therein through which a turbine rotorshaft 12 extends. The aperture 11 is considerably larger in diameterthan that of the rotor shaft 12 and there is further provided a glandstructure generally designated 14 which gland structure may be of anysuitable and well known design or type. As well known in the art, thehousing 10 defines an exhaust space 15 and, in operation, steam employedto motivate the rotor shaft 12 fills this space after expansion. Therotor shaft 12 is also only fragmentally shown, however, as well knownin the art, it is provided with the usual turbine blades (not shown) forexpanding and extracting energy from the steam to drive the rotor shaft12 for power generation purposes. Since the steam pressure within thehousing 10 is lower than that of the atmosphere externally of thehousing, the gland structure 14 is employed to minimize or restrict theleakage of atmospheric air along the shaft 12 through the aperture 11 tothe space 15, as well known in the art.

The gland structure 14 is of generally circular cross sectional shape.Accordingly, no cross sectional view thereof is shown or is thought tobe required for comprehension. The gland structure 14- is provided withwall structure 14a defining a first space 16 and a second space 17 ofgenerally annular shape and separated from each other by annular wallstructures 18, 19 and 20 jointly defining an axially extending opening21 of slightly larger diameter than that of theshaft 12. The opening 21is substantially restricted by a plurality of labyrinth seal members 23,24, 25 and 26 disposed in slightly radially spaced relation with theouter circumference of the shaft 12. Accordingly, it will be understoodthat leakage along the outer surface of the shaft 12 is substantiallyminimized but not absolutely prevented.

To prevent the flow of air from the atmosphere along the shaft 12 to theinside of the housing, there is pro vided a steam supply conduit 27 foradmitting sealing steam into the space 16 at a sufliciently highpressure to oppose the atmospheric air pressure. The steam conduit 27 isprovided with a suitable connecting ferrule 28 to provide a leakproofconnection at the gland 14.

The gland walls 18, 19 and 21) are disposed in axially spacedrelationship with each other. Hence, as the sealing steam flows into thespace 16, it is free to move along the shaft 12 in two directions. Morespecifically, it is allowed to flow through the labyrinth sealstructures 24 and 23 into the housing and also along the shaft 12 beyondthe seal structure 25 and thence into the space 17. The gland 14 isfurther provided with an outlet conduit 29 disposed in communicationwith the space 17. The conduit 29 is connected to a suitable region oflower pressure than that of the space 17 and the external atmosphere sothat preferential flow of steam from the space 17 is established throughthe conduit 29 to the region of lower pressure. Accordingly, as wellknown in the art, the leakage of this sealing steam beyond the labyrinthseal 26 to the external atmosphere is prevented.

Steam for sealing the gland structure may be obtained from any suitablesupply. However, for economic and expediency reasons it is usuallyprovided from a region in the steam turbine cycle operating at a highertemperature and pressure value than that of the steam within the turbinehousing 10. Accordingly, such steam is directed into the conduit 27, asindicated by the arrow 30, at a higher temperature value than requiredor desired, and is reduced to the required degree before admission tothe gland space 16. More particularly, the temperature of the sea ingsteam in the gland space 16 must be at a higher value than that of thesteam within the turbine housing, thereby to minimize the possibility ofcondensation and consequent erosion of the turbine rotor 12 and glandseals 23, 24, and as well as shock upon the rotor shaft 12 by sudden andlocalized chilling thereof with the possibility of warping. Hence, it isessential that the temperature of the sealing steam be maintained abovea minimum safe value so that the formation of moisture or condensate inthe gland structure 14 is prevented. It is also essential to insure thatthe temperature of the steam be maintained below a predetermined safevalue to prevent overheating of the shaft 12.

In accordance with the invention, there is provided apparatus forreducing the temperature of the steam within an acceptable rangeincluding a minimum safe value and arnaximum safe value. This apparatusincludes an injector or spray nozzle 32 disposed within the conduit 27and connected to a suitable supply of water (not shown) by suitableconduits 33 and 34-. There is further provided a primary value structure'36 disposed in the conduit and arranged in a manner to control the rateof flow of water through the conduits 34 and 33 to the injector 32,thereby to vary the amounts of liquid injected into the conduit 27 withattendant vaporization of the liquid and cooling of the steam to thedesired degree in a manner which will hereinafter be more fullydescribed.

As illustrated, the value 36 is of the pneumatically actuated diaphragmtype and is spring biased to the open or unblocking position but ismovable towards the closed or blocking position in response to thepressure of air admitted thereto. Hence, in the event of failure ormalfunction, the valve will tend to move to the open position, therebypermitting the water to flow to the injector 32 at maximum rate.

There is provided a secondary valve structure 38 disposed downstream ofthe valve 36 in the conduit 33. This valve structure, as illustrated, isalso of the same pneumatically operabe diaphragm type as valve 36, butis biased to the blocking position. Hence, in the event of failure ofthis valve, liquid to the injecting nozzle 32 would be interrupted, eventhough the valve 36 is in the fully open position. In normal operation,the secondary valve 38 is maintained in the open position by pneumaticfluid pressure acting thereon and directed thereto by a conduit 39.

There is further provided an emergency valve structure 40 interposed inthe conduit 39 for controlling the fluid flow to the valve structure 38.This valve structure 40, as illustrated, is of the electrically actuatedtype and is provided with a solenoid structure 41 for actuation. Thevalve structure 40 is provided with a venting port 42 for bleeding theair trapped in the conduit 39 to the atmosphere, as indicated by thearrow 43, through an outlet 44, and the valve is so designed that innormal operation (without energization) the venting port 42 is blockedand fluid from a conduit 45 is directed through the valve structure 40to the conduit 39. Fluid (such as air) for actuating the valves 38 and36 is admitted into the system from any suitable supply (not shown) by aconduit 46 having a filter F interposed therein and branching downstreamtherefrom into a branch conduit 47 leading to the valve structure 40 anda branch conduit 48 leading to the conduit 37 by way of a conduit 49 anda suitable variable air pressure controlling structure 50. The airsupplied to the conduit 46 may vary in pressure within a wide range.Accordingly, there are provided pressure regulating valves 51 and 52 inthe conduits 48 and 47, respectively to maintain the pressure of the airto the valve structures 33 and 36 at constant prescribed operatingpressure levels.

The pressure controller 50, as illustrated, is provided with a nozzle 53interposed between the conduits 49 and 37 and having a restricted outlet54 disposed in close proximity to a Bourdon tube structure 55. Aswellknown in the art, the controller 50 is effective to modify thepressure of the air elivered to the valve 36 by movement of the Bourdontube 55 towards or away from the nozzle outlet 54, thereby varying therate of bleeding of the air to the atmosphere.

Within the gland 14 there is provided a thermal sensing device 57,which, as illustrated, is of the vaporizable liquid filled bulb type,connected to the Bourdon tube 55 by a suitable capillary tube 58. Inoperation, as the sensing bulb 57 becomes heated, the vapor pressureformed therein is effective to distend the Bourdon tube 55 to acorresponding degree, thereby controlling the rate of bleed through thenozzle outlet 54 and the pressure acting on the valve 36, in a mannerwell known in the art.

In operation, as thus far described, the apparatus is effective tocontrol the rate of water injection into the conduit 27 as follows.Assuming the steam turbine is of the low pressure type in which thetemperature of the steam within the space 15 is normally maintainedbetween 60 F. and 100 F., so that the average is about F., it is desiredto maintain the temperature of the sealing steam admitted to the glandspace 16 within a minimum and maximum safe range, for example 250 to 350F. Accordingly, the thermal sensing bulb 57 is effective to sense thetemperature of the steam in the space 16 and to regulate the Bourdontube 55 in a manner to control the pressure of the air delivered throughthe conduit 37 to the primary valve 36, in such a manner that theprimary valve structure 36 is effective to regulate the flow of liquidtherethrough to the water injector 32 at the rate required to maintainthe temperature of the sealing steam within this range. Moreparticularly, should the value of the steam in the space 16 approach themaximum safe value of 350 F., the increased vapor pressure of thethermal sensing bulb 57 is effective to distend or flex the Bourdon tubeaway from the nozzle outlet 54, thereby bleeding more air to atmosphereand reducing the pres sure in the valve structure 36. The valve 36 isthus pef= mitted to move to a more open position thereby increas ing therate of Water injection by the injectior 32, cooling; the steam flowingtherepast to a greater degree, and there by reducing the temperature ofthe sealing steam in the space 16.

Conversely, should the temperature of the sealing steam in the space 16approach the minimum safe value of 250 F., the reduced vapor pressure inthe thermal sensing bulb 57 will permit the Bourdon tube 55 to contract,thereby restricting flow of the air through the outlet conduit 54 andbuilding up the pressure of the fluid through the conduit 37 to thevalve 36. Accordingly, the valve 36 is urged toward the closed orblocking position, thereby restricting the flow of the liquidtherethrough to the injector 32 and permitting the temperature of thesteam in the space 16 to rise.

During such operation, the air pressure in the conduit 47 and the valve40 is effective to maintain the secondary valve 38 in the open positionand permit the water to flow therepast under the control of the primaryvalve 36.

However, in the event of malfunction of the pressure controller 50 orthe primary valve structure 36, for any reason, the valve 36 will beurged to the wide open position by its spring bias and thereby beineflective to regu late the flow of water to the injector 32 asrequired.-

Should this happen, the rate of water injection may be so excessive thatwater droplets might be directed through the space 16 and the seals tothe shaft structure 12 with attendant sudden thermal shock to the shaftstructure and localized chilling causing bowing or warping thereof.

Accordingly, there is further provided a second thermal sensing device60 disposed in the space 16 and etfective to sense the temperature ofthe steam therein. As illustrated, the thermal sensing device 60 is ofthe ditferential expansion type and includes a tubular shell structure61 having an elongated rod 62 disposed therein. The shell structure 61is rigidly fastened to the gland structure 14 in any suitable manner andthe free end of the rod 62 extends into abutment with a switch lever 63provided in an electrical control device 64. The lever 63 is fulcrumedat 65 intermediate its two ends and is provided with three sets ofelectrical contacts 66, 67 and 68 movable into and out of abutment withstationary mating contacts 69, 70 and 71. The stationary contacts 70 and71 are disposed above the lever 63, while the stationary contact 69 isdisposed below the lever 63. The lever 63 is biased into abutment withthe elongated rod 62 by a suitable spring 72 and in normal operation(within the minimum and maximum safe temperatures) the movable contactsare disposed in spaced relation with the stationary contacts, asillustrated.

The shell structure 61 has a greater thermal expansion coefiicient thanthat of the rod 62, so that with a rise in temperature of the space 16the rod 62 will move in upward direction, thereby permitting the lever63 to rotate clockwise while, when the temperature within the space 16falls the rod 62 will move downwardly and is eifective to rotate thelever 63 in the opposite direction or towards the stationary contacts 70and 71. The thermal sensing device 60 and the electrical control 64 areso arranged and calibrated that upon rise in temperature of the steam inthe space 16 to above the safe value of 350 F., the contact 66 is movedinto abutment with the contact 69 and conversely, when the value of thesteam in the space 16 falls to the minimum safe value of 250 F. thecontacts 67 and 68 are moved into abutment with the stationary contacts70 and 71.

The solenoid 41 of the emergency valve 40 and electrical alarm devices74 and 75 are interconnected in electrical circuitry which is energizedfrom any suitable electrical supply, as indicated by the conductors '76and 77, and controlled by the control device 64. The movable contacts 67and 68, as well as the stationary contact 69, are connected in parallelto the conductor 77, and the solenoid 41 is interconnected between thestationary contact 71 and the conductor '76 by a pair of suitableconductors 78 and 79. The electrical alarm 75 for example, a lamp, isconnected to the stationary contact 70 and to the conductor 76 bysuitable conductors 80 and 81. Hence, it will be seen that the lamp 75and the solenoid 41 are disposed in parallel with each other andarranged in such a manner that when the switch lever 63 is rotated incounterclockwise direction by the thermal sensing rod 62 in response toa reduction in steam temperature in the space 16, circuits areestablished jointly through the solenoid 41 and the lamp 75. During suchconditions, the solenoid is energized to actuate the emergency valve 40to the air blocking position, thereby interrupting the flow of air fromthe conduit 47 to the valve 38 andpermittmg the air trapped in the valve38 and the conduit 39 to be vented to the atmosphere through the outlet44. S multaneously therewith, the lamp 75 is energized to provide avisual warning of such an event.

It will also now be seen that when the switch lever 63 is rotated in theclockwise direction by the elongated rod 62 in response to a steamtemperature within the space 16 of above 350 F., the movable contact 66is moved into abutment with the stationary contact 69, therebyinterrupting the circuit through the solenoid 41 and the lamp 75, andestablishing a circuit through the alarm device 74, for example, a bell,to provide an audible warning of such event.

More specifically, in the event of failure of the primary system andmovement of the primary control valve 36 to the Wide open position withattendant greatly increased flow of water injection into the steamconduit 27, as previously described, the temperature of the resultingsteam in the space 16 may rapidly fall below the minimum safe value of250 F. This condition is sensed by the thermal sensing device 60, withattendant establishment of the circuit through the solenoid 41 to effectmovement of the valve 38 to the water flow blocking position, therebyinterrupting flow of the water to the injector 32, and initiation of avisible alarm to the operator of such a state or condition, byenergization of the lamp 75.

In the event that, for any reason, the emergency valve structure 40should fail to operate as required, the valve 38 may move to theblocking position, thereby interrupting the flow of water to theinjector 32 with attendant rise in temperature of the sealing steam inthe space 16. Should such an event occur, the thermal sensing device 68is effective to move the switch lever 63 in clockwise direction therebyestablishing a circuit. through the alarm 'bell 74 to provide a warningto the operator of such a condition.

In such an event it might be necessary to shut down the apparatus ortake any other steps that are necessary to remedy the situation.

If desired, the conduit 34 may be provided with a pair of suitablenormally open manually operated valves 82 and 83 and a bypass line 84having a normally closed manually operated valve 85 may be provided tocircumvent the primary valve 36. During an emergency where in the valve36 fails in the open position and the valve 38 fails in the openposition, the flow of water to the injector 32 may be regulated byeither the valve 82 or 83, as required. However, in the event that it isdesired to repair the valve 36 while maintaining the sealing steam andgland structure in operation, the two valves 82 and 83 may be rotated tothe blocking position and the water injection may then be controlledmanually by regulation of the valve 85 in the bypass line 84.

Although only one embodiment of the invention has been shown anddescribed, it will be obvious to those skilled in the art that it is notso limited, but is susceptible of various other changes andmodifications without de parting from the spirit thereof.

We claim as our invention:

1. Apparatus for regulating the temperature of steam for sealing a steamturbine gland structure, comprising means including a conduit connectedto said gland structure,

means for admitting steam to said conduit at a temperature higher thanrequired by said gland structure, means for injecting water into saidconduit to cool said steam,

primary means including a primary thermostatically controlled valve forregulating the rate of water in jection in a manner to cool the steam toa predeter mined range of temperature including a maximum safetemperature and a minimum safe temperature, and

secondary means including a secondary thermostaticab ly controlled valvefor interrupting the water injection in the event that the steamtemperature falls below said minimum safe temperature.

2. The structure recited in claim 1 and further includ means responsiveto a temperature exceeding the maximum safe temperature for initiatingan alarm.

3. The structure recited in claim 1, and further including primarythermal sensing means for controlling the primary valve,

secondary thermal sensing means for controlling the secondary valve, and

means actuated by said secondary thermal sensing means for initiating analarm signal indicative of a steam temperature exceeding the maximumsafe temperature.

4. Apparatus for regulating the temperature of steam for sealing aturbine gland structure, comprising means including a first conduit fordelivering steam to said gland structure;

means for admitting steam to said first conduit at a temperature higherthan required by said gland structure;

means including a second conduit for injecting water into said firstconduit to cool said steam;

a primary system for controlling the rate of water injection in a mannerto cool the steam to a predetermined range of temperature including amaximum safe temperature and a minimum safe temperature;

said primary system including a first valve disposed in said secondconduit;

means including first thermal sensing means for detecting thetemperature of said gland structure and effective to control the degreeof opening of said first valve;

a secondary system for overriding said first system in the event ofmalfunction of the latter;

said secondary system including a normally open second valve disposed insaid second conduit; and

means including a second thermal sensing means for detecting thetemperature of said gland structure and effective to actuate said secondvalve to the closed position, when the temperature of the glandstructure falls below the minimum safe temperature, thereby interruptinginjection of Water.

5. The structure recited in claim 4, and further including meansproviding an alarm signal, and

means actuated by the second thermal sensing means to actuated saidalarm means when the temperature of the gland structure exceeds themaximum safe temperature.

6. The structure recited in claim 4, in which the first and secondvalves are actuated by pressurized fluid, and further including thirdconduit means for delivering pressurized fluid to the second valve,

said second valve is normally maintained in the open position by thepressurized fluid, and

a solenoid valve disposed in said third conduit and electricallyactuable from a fluid conducting position to a fluid blocking positionwhen the temperature of the gland structure falls below the minimum safetemperature.

No references cited.

MARTIN P. SCHWADRON, Primary Examiner.

ROBERT R. BUNEVICH, Examiner.

1. APPARATUS FOR REGULATING THE TEMPERATURE OF STEAM FOR SEALING A STEAMTURBINE GLAND STRUCTURE, COMPRISING MEANS INCLUDING A CONDUIT CONNECTEDTO SAID GLAND STRUCTURE, MEANS FOR ADMITTING STEAM TO SAID CONDUIT AT ATEMPERATURE HIGHER THAN REQUIRED BY SAID GLAND STRUCTURE, MEANS FORINJECTING WATER INTO SAID CONDUIT TO COOL SAID STEAM, PRIMARY MEANSINCLUDING A PRIMARY THERMOSTATICALLY CONTROLLED VALVE FOR REGULATING THERATE OF WATER INJECTION IN A MANNER TO COOL THE STEAM TO A PREDETERMINEDRANGE OF TEMPERATURE INCLUDING A MAXIMUM SAFE TEMPERATURE AND A MINIMUMSAFE TEMPERATURE, AND SECONDARY MEANS INCLUDING A SECONDARYTHERMOSTATICALLY CONTROLLED VALVE FOR INTERRUPTING THE WATER INJECTIONIN THE EVENT THAT THE STEAM TEMPERATURE FALLS BELOW SAID MINIMUM SAFETEMPERATURE.